Upgrade Gradle to Version 7.5.1

[charlestian23]

Description

Re-attempting certain changes made in #401.

• Upgraded Gradle to 7.5.1
• Added gradle.properties to show Gradle deprecation warnings when compiling
• Updated code to no longer use deprecated Gradle features
• Added a GitHub action to deploy javadocs to GitHub Pages, hosted off the javadoc branch

Note: I did not attempt to update or remove some dependencies in this pull request. I will do that in a separate pull request in the future; however, I am not prioritizing that right now.

Closes #289

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (improvement to an already existing feature)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

The jar file seems to compile. Since I did not change any of the source code, this should be sufficient.

Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes